Visit your local RV dealerships first and look at all models, both new and used. This will give a good "feel" for what you like and don't like. Then, if you do find one, for example used, at one of the dealerships, see if you can find a comparable through your private enterprises. This will give you the biggest bang for your buck (especially in time). Now if you cannot find a comparable in the private sector, then you always the option to negotiate with the dealer.
However, before doing any of that, you should start exploring the various RV web sites. Here is a link that give a pretty good list of almost every manufacturer "out there". Click the links and go directly to that RV brand. It's a great starting place, and maybe a bit overwhelming too.
Click hereIn selecting your RV, you really need to narrow down your choices, and personal wants. That's why visiting some dealerships is a great help. Actually going inside the models is much more revealing than anything on-line.